Flame resistant fiber blend and fabrics made therefrom

ABSTRACT

A flame retardant or flame resistant (FR) fiber blend is provided that comprises amorphous silica fibers and at least one FR fiber. A flame retardant fabric, manufactured from a blend of fibers comprises amorphous silica fibers and at least one FR fiber. Barrier fabrics, manufactured from a blend of fibers, are provided comprising amorphous silica fibers and at least one FR fiber.

CROSS-REFERENCE TO RELATED APPLICATIONS

None

BACKGROUND OF THE INVENTION

This invention relates to a flame resistant fiber blend useful in preparing fabrics having flame resistance and particularly non-woven flame resistant materials such as barrier fabrics.

Flame retardant or flame-resistant materials (FR) are employed in many textile applications. For example, FR materials are useful as barrier layers between the exterior fabric and the inner stuffing of furniture, comforters, pillows, and mattresses. Such materials can be woven or non-woven, knitted, or laminated with other materials.

The flame-resistance or flame-retardant properties of such FR materials are typically determined according to various standard methods, such as California TB117 and TB 133 for upholstery; NFPA701 for curtains and drapes; California Test Bulletin 129, dated October 1992, concerning flammability test procedures for mattresses in public buildings, and California Test Bulletin 603 concerning mattresses for residential use. Desirably, the FR material does not melt or shrink away from the flame, but forms a char that helps control the burn and shield the materials surrounded by the fabric.

Other desirable properties of FR barrier fabrics include a white color so as to not contaminate the manufacturing facility or change the look of the composite article; unaffected by ultraviolet light so as not to yellow and change the look of light-colored mattress ticking or upholstery fabrics; soft to the touch, thereby imparting the feel desired by the consumer; and cost effectiveness.

Some fibers are known to have FR properties, such as halogen-containing, phosphorus-containing, and antimony-containing materials. These materials, however, are heavier than similar types of non-FR materials, and they have reduced wear life. Fiberglass flame barriers have poor durability due to glass-to-glass abrasion.

There is still a need in the industry to create non-woven barrier fabric that can pass the stringent flammability testing guidelines. Moreover, there is a need in the industry to produce such a non-woven article from materials that are relatively inexpensive and have light batt weights. Additionally, other industries would benefit from the availability of flame resistant fabrics, made from fibers having flame resistant or flame retardant properties, to use in lieu of fabrics that do not have such properties.

BRIEF SUMMARY OF THE INVENTION

It is therefore, an aspect of the present invention to provide a flame retardant or flame resistant fiber blend that can be used to prepare non-woven fabric with good char strength.

It is another aspect of the present invention to provide a flame retardant or flame resistant fiber blend that can elevate the char strength of more commonly known flame retardant fibers.

It is another aspect of the present invention to provide a flame retardant fiber that is white, is less costly than existing fibers and that does not char and, that can be used to prepare non-woven barrier fabrics.

It is another aspect of the present invention to provide a light weight barrier fabric that has good char strength.

It is another aspect of the present invention to provide a barrier fabric having good char strength and lower cost than comparable fabrics comprising melamines, aramids and novoloids.

It is another aspect of the present invention to provide light weight fabrics that have good char strength.

It is another aspect of the present invention to provide fabrics having good char strength and lower cost than comparable fabrics comprising melamines, aramids and novoloids.

At least one or more of the foregoing aspects, together with the advantages thereof over the known art relating to FR fabrics, which shall become apparent from the specification which follows, are accomplished by the invention as hereinafter described and claimed.

In general, the present invention provides a flame retardant or flame resistant fiber blend comprising amorphous silica fibers and at least one FR fiber.

The present invention further provides a barrier fabric manufactured from a blend of fibers comprising amorphous silica fibers and at least one FR fiber.

The present invention further provides a flame retardant fabric manufactured from a blend of fibers comprising amorphous silica fibers and at least one FR fiber.

Advantageously, it has been discovered that fiber blends containing amorphous silica show improved char strength when formed into non-woven fabric, compared to non-woven fabric not containing amorphous silica. The strength to weight ratio of non-woven fabric containing amorphous silica is also improved, when compared to non-woven fabric containing other fibers conventionally used to improve char strength, such as para aramid fibers and melamine fibers.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing FIGURE is a perspective view exploded to show assembly of a tuft button test apparatus.

DETAILED DESCRIPTION OF THE INVENTION

The fiber blend of the present invention comprises amorphous silica fibers and at least one type of FR fiber. Any amorphous silica fiber that improves the char strength when added to a fiber blend may be used. Preferably, the silica fibers are substantially amorphous. While the fibers may contain some crystalline material, a substantial amount of crystallinity is not preferred, because a brittle crystalline structure creates health problems when sharp, fragmented particles are inhaled.

In one embodiment, the silica fiber is chopped fiber derived from E-glass, which has a high content of SiO₂, generally at least 50 to 55 percent and up to about 85 percent. Preferred amorphous silica is prepared from a precursor having a high SiO₂ content. Preferably, the fibers have a diameter of from about 6 to about 13 mkm, and a length of from about 2 to about 4 inches (5 to 10 centimeters). Suitable silica fiber is commercially available, for example from Polotsk-Steklovolokno, Belarus, through their U.S. agent TMS in Sparks, Nev.

The amount of silica fiber in the blend can vary, depending upon the other fibers used. In one embodiment, the amount of silica fiber in the blend is preferably from about 5 to about 65 weight percent, based upon the total weight of the blend, more preferably from about 15 to about 50 weight percent, and even more preferably from about 20 to about 30 weight percent.

The fiber blend of the present invention also includes at least one FR fiber. Various FR fibers are known in the art. The FR fibers employed in the fabrics of the present invention may be an inherent flame resistant fiber or a fiber (natural or synthetic) that is coated with an FR resin. The inherent flame resistant fibers are not coated, but have an FR component incorporated within the structural chemistry of the fiber. The term FR fiber, as used herein, includes both the inherent flame resistant and flame retardant fibers as well as fibers that are not inherently flame resistant or flame retardant, but are coated with FR resins. Accordingly, by way of example, a polypropylene fiber coated with an FR resin would be an FR polypropylene fiber.

Suitable inherently flame resistant fibers include polymer fibers having a phosphorus-containing group, an amine, a modified aluminosilicate, or a halogen-containing group. Examples of inherently flame-retardant fibers include melamines, meta-aramids, para-aramids, polybenzimidazole, polyimides, polyamideimides, partially oxidized polyacrylonitriles, novoloids, poly(p-phenylene benzobisoxazoles), poly (p-phenylenebenzothiazoles), polyphenylene sulfides, flame retardant viscose rayons; (e.g., a viscose rayon based fiber containing 30% aluminosilicate modified silica, SiO₂+Al₂O₃), polyetheretherketones, polyketones, polyetherimides, and combinations thereof).

Melamines include those sold under the tradenames Basofil by McKinnon-Land-Moran LLC. Meta-aramids include poly (m-phenylene isophthalamide), for example sold under the tradenames NOMEX® by E.I. Du Pont de Nemours and Co., TEIJINCONEX® and CONEX® by Teijin Limited and FENYLENE® by Russian State Complex. Para-aramids include poly (p-phenylene terephthalamide), for example sold under the tradename KEVLAR® by E.I. Du Pont de Nemours and Co., and poly (diphenylether para-aramid), for example sold under the tradename TECHNORA® by Teijin Limited, and under the tradenames TWARON® by Acordis and FENYLENE ST® (Russian State Complex).

Polybenzimidazole is sold under the tradename PBI by Hoechst Celanese Acetate LLC. Polyimides include those sold under the tradenames P-84® by Inspec Fibers and KAPTON® by E.I. Du Pont de Nemours and Co. Polyamideimides include for example those sold under the tradename KERMEL® by Rhone-Poulenc. Partially oxidized polyacrylonitriles include, for example, those sold under the tradenames FORTAFIL OPF® by Fortafil Fibers Inc., AVOX® by Textron Inc., PYRON® by Zoltek Corp., PANOX® by SGL Technik, THORNEL® by American Fibers and Fabrics and PYROMEX® by Toho Rayon Corp.

Novoloids include, for example, phenol-formaldehyde novolac, such as that sold under the tradename KYNOL® by Gun Ei Chemical Industry Co. Poly (p-phenylene benzobisoxazole) (PBO) is sold under the tradename ZYLON® by Toyobo Co. Poly (p-phenylene benzothiazole) is also known as PBT. Polyphenylene sulfide (PPS) includes those sold under the tradenames RYTON® by American Fibers and Fabrics, TORAY PPS® by Toray Industries Inc., FORTRON® by Kureha Chemical Industry Co. and PROCON® by Toyobo Co.

Flame retardant viscose rayons include, for example, those sold under the tradenames LENZING FR® by Lenzing A. G. and VISIL® by Sateri Oy Finland. Polyetheretherketones (PEEK) include, for example, that sold under the tradename ZYEX® by Zyex Ltd. Polyketones (PEK) include, for example, that sold under the tradename ULTRAPEK® by BASF. Polyetherimides (PEI) include, for example, that sold under the tradename ULTEM® by General Electric Co.

Modacrylic fibers are made from copolymers of acrylonitrile and other materials such as vinyl chloride, vinylidene chloride or vinyl bromide. Flame retardant materials such as antimony oxide can be added to further enhance flame resistant property. Modacrylic fibers used in this invention are manufactured by Kaneka under the product names KANECARON PBX and PROTEX-M, PROTEX-G, PROTEX-S and PROTEX-PBX. The latter products contain at least 75% of acrylonitile-vinylidene chloride copolymer. SEF PLUS by Solutia is a modacrylic fiber as well with flame retardant properties.

Further examples of inherent FR fibers suitable for use in the blend of the present invention include polyester with phosphalane such as that sold under the trademark TREVIRA CS® fiber or AVORA® PLUS FIBER by KoSa.

Also useful are chloropolymeric fibers, such as those sold under the tradenames THERMOVYL® L9S & ZCS, FIRBRAVYL® L9F, RETRACTYL® L9R, ISOVYL® MPS by Rhovyl S. A., PMACID®, Thueringische, VICLON® by Kureha Chemical Industry Co., TEVIRON® by Teijin Ltd., ENVILON® by Toyo Chemical Co., VICRON®, SARAN® by Pittsfield Weaving, KREHALON® by Kureha Chemical Industry Co., OMNI-SARAN® by Fibrasomni, S. A. de C. V., and combinations thereof. Fluoropolymeric fibers such as polytetrafluoroethylene (PTFE), poly(ethylene-chlorotrifluoroethylene (E-CTFE), polyvinylidene fluoride (PVDF), polyperfluoroalkoxy (PFA), and polyfluorinated ethylene-propylene (FEP) and combinations thereof are also useful.

Natural or synthetic fibers coated with an FR resin are also useful in the fiber blend of the present invention. Suitable fibers coated with an FR resin include those where the resin contains one or more of phosphorus, phosphorus compounds, red phosphorus, esters of phosphorus, and phosphorus complexes; amine compounds, boric acid, bromide, urea-formaldehyde compounds, phosphate-urea compounds, ammonium sulphate, or halogen based compounds. Non-resin coatings like metallic coating are not preferred for the present invention, because they tend to flake-off after continuous use of the product. Suitable commercially available FR resins are sold under the trade names GUARDEX FR®, and FFR® by Glotex Chemicals in Spartanburg, S.C.

The manner in which the resin is coated onto the fiber is not particularly limited. In one embodiment, the FR resin is a liquid product that can be applied as a spray. In another embodiment, the FR resin is a solid that may be applied as a hot melt product to the fibers, or as a solid powder that is then melted into the fibers. In one embodiment, the FR resin is applied to the fibers in an amount of from about 6 to about 25 weight %, based upon the total weight of the coated fibers.

The amount of coated FR fiber in the blend can vary, but is preferably from about 35 to about 95 weight percent, based upon the total weight of the blend, more preferably from about 40 to about 90 weight percent, even more preferably from about 45 to about 85 weight percent.

The denier of the FR fibers is preferably from about 1.5 to about 15 dpf (denier per filament). The foregoing listing of FR fibers is not to be construed as a limiting the practice invention but instead to illustrate the fact that any FR fiber known can be employed with an amorphous silica fiber and utilized in the practice of the present invention. Thus, fiber types includes multifilament and monofilament yarns, having a variety of cross-sections and shapes as well a fibrillated yarns, typically manufactured from slit film tapes.

The fiber blend of the present invention may further contain one or mote non-FR fibers. The non-FR fibers may be synthetic or natural fibers. Suitable non-FR synthetic fibers include polyester such as polyethylene terephthalate (PET); cellulosics, such as rayon and/or lyocell; nylon; polyolefin such as polypropylene fibers; acrylic; melamine and combinations thereof. The lyocell fibers are a generic classification for solvent-spun cellulosic fibers. These fibers are commercially available under the name TENCEL®. Natural fibers include flax, kenaf, hemp, cotton and wool. In one embodiment, non-FR fibers are employed to enhance certain characteristics such as loft, resilience or springiness, tensile strength, and thermal retention.

The fiber blend includes amorphous silica fiber and at least one type of FR fiber. Therefore, the present invention is embodied by a fiber blend that contains amorphous silica fiber, an FR fiber, optionally additional FR fibers, and optionally one or more non-FR fibers. In one embodiment, the fiber blend includes: modacrylic fiber; a cellulosic fiber, lyocell, and amorphous silica fiber.

In another embodiment, the fiber blend further includes more than one type of FR fiber. In a preferred embodiment, the fiber blend includes amorphous silica fiber, modacrylic fiber, and VISIL. In yet another embodiment, the fiber blend includes modacrylic fiber, FR rayon fiber, and amorphous silica fiber.

In another embodiment, the fiber blend includes modacrylic fibers, VISIL (FR viscose rayon) fibers, amorphous silica fibers, and FR polypropylene fibers. The amounts of each component can vary however, advantageous char strength is obtained when a needlepunched fabric is prepared from a blend containing about 40 weight percent modacrylic, about 40 weight percent VISIL, about 15 weight percent amorphous silica, and about 5 weight percent FR polypropylene fibers.

The fibers of the present invention can be used to manufacture fabrics, where FR properties are desired or would be useful. Essentially any type of fabric, produced from fibers, such as nowoven fabrics; woven fabrics, both open and closed weave; knitted fabrics and various laminates can be made using the fibers of the present invention. The manufacture of such fabrics is not limited to a particular method or apparatus.

The nonwoven fabric of the present invention may be produced by mechanically interlocking the fibers of a web. The mechanical interlocking is preferably achieved through a needlepunch operation. Needlepunch methods of preparing non-woven fabric are known in the art. In one embodiment, the nonwoven fabric, sometimes called a batt, may be constructed as follows: the fiber blend is weighed and then dry laid/air laid onto a moving conveyor belt. The speed of the conveyor belt can be adjusted to provide the desired batt weight. Multiple layers of batts are fed through a needle loom where barbed needles are driven through the layers to provide entanglement.

There are several other known methods for producing nonwoven fabrics including hydroentanglement (spunlace), thermal bonding (calendering and/or though-air), latex bonding or adhesive bonding processes. The spunlace method is similar to needlepunch except waterjets are used to entangle the fibers instead of needles. Thermal bonding requires either some type if thermoplastic fiber or powder to act as a binder. It is to be appreciated that all forms of novwovens can be made with the FR fiber blends of the present invention to produce barrier fabrics having FR properties. Accordingly, reference to nonwoven fabrics herein includes all forms of manufacture.

Suitable nonwoven fabrics of the present invention have a batt weight greater than about 2.25 oz./sq. yd. (osy) Preferably the batt weight ranges from about 2.25 osy to about 20 osy, more preferably about 3.5 osy. In one embodiment, the fibers are carded. Then the conveyor belt moves to an area where spray-on material may optionally be added to the nonwoven batt. For example, the FR resin may be sprayed onto the nonwoven batt as a latex. In one embodiment, the conveyor belt is foraminous, and the excess latex spray material drips through the belt and may be collected for reuse later. After the optional spraying, the fiber blend is transported to a dryer or oven. The fibers may be transported by conveyer belt to the needlepunch loom where the fibers of the batt are mechanically oriented and interlocked to form a non-woven fabric.

The non-woven FR fabric is useful as a barrier fabric for bedding materials and bed clothing. The fabric is also useful in upholstery and drapery applications where flame resistance is desired. Additionally, fabrics other than non-wovens can be made from the fibers of the present invention, where an FR fabric is desired.

GENERAL EXPERIMENTAL

In order to demonstrate the efficacy of various fiber blends as FR materials, a number of samples were prepared and tested, as described hereinbelow. The examples have been provided to demonstrate practice of the present invention and should not be construed as limitations of the invention or its practice.

EXAMPLES Example Nos. 1-12

The samples were prepared on a miniature card and needleloom. The fiber was first hand-opened and layered on the card feed apron. The carded sample was run back through the card a second time to assure intimate blending of fibers. The carded web, layered around the wind-up roll, was cut transversely and removed from the card. Then it was fed into the needlepunch line for needling. A second pass was performed to accomplish needling from the opposite side.

Standard tensile strength testers were modified to measure the char strength of the barrier fabric of the present invention. More specifically, the fabric stiffness test typically used with pocket coil material was modified to measure the amount of force, measured and reported in pounds, required to push a fabric sample through a hole with a plunger. To force the material to break, a template was fabricated so that the fabric could be sandwiched between the template and the existing test plate.

Specimens of the barrier fabric were cut into 4″ by 8″ (10 by 16 cm) samples and weighed. The samples were placed in a charring frame and charred by using a Bunsen burner. The frame was then mounted into the modified stiffness tester and the char strength of the sample was measured. Table 1 summarizes the results for Example Nos. 1-12. As a standard, a blend comprising 40% modacrylic and 60% Visil was selected (Ex. No. 1). The following types of fiber were used: Basofil® (abbreviated Bas); modacrylic fiber KANECARON PBX; VISIL® (abbreviated Vis); polyethylene terephthalate (abbreviated PET); and amorphous silica (abbreviated Sil). Examples 2-8 and 10-11 are comparative examples of fabric prepared from various fiber blends as indicated. Examples 2 and 3 contained 10% Basofil fibers as a replacement for equal amounts of modacrylic fiber or Visil fiber; Examples 4 and 5 contained 10% and 20% PET fibers as a replacement for equal amounts of Visil fiber; Example 6 comprised a blend 10% Basofil fibers with PET fibers, modacrylic fiber and Visil fiber; Examples 7 and 8 contained 10% and 15% PET fibers as a replacement for varying amounts of modacrylic fiber and Visil fiber; Examples 10 and 11 contained 10% Basofil fibers as a replacement for varying amounts of modacrylic fiber and Visil fiber; Examples 9 and 12 were prepared from fiber blends containing amorphous silica fibers, according to the present invention. TABLE 1 CHAR STRENGTH TO WEIGHT RATIO FOR NON-WOVEN FABRIC MADE FROM VARIOUS FIBER BLENDS Ex. Strength Weight Strength/ No. FIBER BLEND (pounds) (ounces) Weight 1 40 PBX/60 Vis 0.32 5.4 0.06 2 10 Bas/30 PBX/60 Vis 0.31 5.9 0.05 3 10 Bas/40 PBX/50 Vis 0.36 6.9 0.05 4 10 PET/40 PBX/50 Vis 0.32 6.7 0.05 5 20 PET/40 PBX/40 Vis 0.32 6.5 0.05 6 10 Bas/10 PET/25 PBX/ 0.32 4.2 0.08 55 Vis 7 10 PET/25 PBX/65 Vis 0.30 4.7 0.06 8 15 PET/25 PBX/60 Vis 0.29 5.0 0.06 9 10 Sil/35 PBX/55 Vis 0.42 5.3 0.08 10 10 Bas/30 PBX/60 Vis 0.30 3.2 0.09 11 10 Bas/40 PBX/50 Vis 0.30 3.3 0.09 12 10 Sil/35 PBX/55 Vis 0.31 2.9 0.10

It can be seen that when the char strength of the fabric is correlated to the weight of the sample, the fabric formed from fiber blends containing amorphous silica (Examples No. 9 and 12) show a strength to weight ratio of from 0.08 to about 0.10.

Example Nos. 13-42

Examples 13-42 were prepared and tested as for Examples 1-12, except that different blends of fiber were used, as summarized in Table 2. Strength of each fabric is reported in pounds, as discussed hereinabove. The fabrics have been reported in six groups of four blends and two groups of three blends. Examples 16, 20, 24, 28, 31, 35, 38, and 42 report a base fabric and the examples immediately preceding report the addition of various types of FR fiber. Char strength, in pounds, was measured and the results have been reported by decreasing values for each group.

For example, FR rayon and modacrylic fibers were used to prepare Example 16, denoted FR Rayon/Modacrylic Base Fabric. Examples 13-15 are variations of this base fabric, because in each case one other type of FR fiber was added: para aramid fibers were added to Example 13, melamine fibers were added to Example 14, and amorphous silica fibers were added to Example 15, according to the present invention.

Similarly, Example 20 was prepared from FR rayon fibers and is denoted FR Rayon Base Fabric, while Examples 17-19 were variations of this base fabric: para aramid fibers were added to Example 17, melamine fibers were added to Example 18, and amorphous silica fibers were added to Example 19, according to the present invention.

Likewise, Example 24 is a rayon/modacrylic base fabric, and Examples 21-23 were variations of this base fabric: melamine fibers were added to Example 21, para aramid fibers were added to Example 22, and amorphous silica fibers were added to Example 23, according to the present invention.

Example 28 is a lyocell/modacrylic base fabric, and Examples 25-27 were variations of this base fabric: para aramid fibers were added to Example 25, melamine fibers were added to Example 26, and amorphous silica fibers were added to Example 27, according to the present invention.

In the next series, Example 31 is the Visil/modacrylic base fabric, and Examples 29, 30 and 32 were variations of this base fabric: para aramid fibers were added to Example 29, amorphous silica fibers were added to Example 30, according to the present invention; and melamine fibers were added to Example 32.

Example 35 is a Visil base fabric, while Examples 33-34 were variations of this base fabric: melamine fibers were added to Example 33, and amorphous silica fibers were added to Example 34, according to the present invention.

Example 38 is a rayon base fabric, while Example 36 contains rayon and melamine, and Example 37 contains rayon and amorphous silica, according to the present invention.

Example 42 is a lyocell base fabric, while Example 39 contains para aramid, Example 40 contains lyocell and melamine, and Example 41 contains lyocell and amorphous silica, according to the present invention. TABLE 2 CHAR STRENGTH OF NON-WOVEN FABRIC MADE FROM VARIOUS FIBER BLENDS Ex. No. FABRIC STRENGTH 13 FR Rayon/Modacrylic/10% para aramid 3.22 14 FR Rayon/Modacrylic/10% melamine 2.39 15 FR Rayon/Modacrylic/10% silica 2.23 16 FR Rayon/Modacrylic Base Fabric 1.77 17 FR Rayon/10% para aramid 2.98 18 FR Rayon/10% melamine 2.37 19 FR Rayon/10% silica 1.39 20 FR Rayon Base Fabric 0.63 21 Rayon/Modacrylic/10% melamine 2.85 22 Rayon/Modacrylic/10% para aramid 2.34 23 Rayon/Modacrylic/10% silica 2.12 24 Rayon/Modacrylic Base Fabric 0.74 25 Lyocell/Modacrylic/10% para aramid 2.37 26 Lyocell/Modacrylic/10% melamine 1.49 27 Lyocell/Modacrylic/10% silica 1.43 28 Lyocell/Modacrylic Base Fabric 0.64 29 Visil/Modacrylic/10% para aramid 2.08 30 Visil/Modacrylic/10% silica 1.76 31 Visil/Modacrylic Base Fabric 1.54 32 Visil/Modacrylic/ 10% melamine 1.32 33 Visil/10% melamine 1.65 34 Visil/10% silica 1.29 35 Visil Base Fabric 0.92 36 Rayon/10% melamine 1.55 37 Rayon/10% silica 1.36 38 Rayon Base Fabric 0.01 39 Lyocell/10% para aramid 1.27 40 Lyocell/10% melamine 0.37 41 Lyocell/10% silica 0.32 42 Lyocell Base Fabric 0.01

It can be seen from the data in Table 2 that fabric containing 10% by weight amorphous silica shows improved char strength as compared to that same base fabric without amorphous silica e.g., Example No. 15 compared to Example No. 16. It will be noted that while the use of other FR materials, namely para-aramid and melamine, with the base fabric generally provided greater strength than the blend containing amorphous silica, the former two materials are far more costly than the silica. In addition, the aramids present a golden yellow color to the fabric, while the melamines present an off-white color. The amorphous silica does neither and thus, the resulting fabric is white without the addition of pigments. Finally, the char strength of the fabrics comprising amorphous silica is more that adequate for usefulness in bedding, clothing, furniture, drapery and related purposes.

Example Nos. 43-50

Examples 43-50 were prepared by using a needlepunch line including a 12 inch card, a crosslapper, and a 24 inch Dilo OD-1 needle loom. Example No. 43 was the base blend (8 osy) comprising 40% modacrylic and 60% Visil) and in the Examples following, various materials or FR fibers were employed. Example 44 comprised a blend of the base blend (79%) and leno weave carpet backing, 2.1 osy, (21%). Example 45 comprised a blend of the base blend (89%) and Conwed scrim, 1 osy, (11%). Conwed is a very lightweight polypropylene material with the “warp” and “fill” monofilaments “welded” together at the vertices to provide a “leno type” appearance. Example 46 comprised a blend of the base blend (85%) and Basofil (melamine) (15%). Example 47 comprised a blend of the base blend (85 %) and Conex (15%). Conex is a meta-aramid. Example 48 comprised a blend of the base blend (85%) and amorphous silica (15%). Example 49 comprised a blend of the base blend (85%) and Kynol (phenol-formaldehyde novolac) (15%). Example 50 comprised a blend of amorphous silica (15%), modacrylic fiber (40%) and Visil fiber (45%). Example No. 50 represents a fabric of the present invention.

A tuft button simulation was designed to expose the charred fabric to stresses that it might see in an actual mattress burn, and gives a pass/fail indication of fabric strength. A small test rig was constructed out of wood. Components were assembled shown in the drawing FIGURE to form tuft button test apparatus 10. Mattress components including 4 inch foam 12, two 1 inch super-soft foams 14,16, barrier fabric 18, which was 0.5 ounces per square foot (osf), PET fiber fill 20, and a PET ticking fabric 22 were assembled as described below, and then burned under tension.

The components were assembled on top of upper plate 24. The foam components 12, 14 and 16, were compressed and the barrier fabric 18, fiber fill 20, and ticking 22 were wrapped around all sides of upper plate 24. Lower plate 26 was positioned to sandwich fabrics 18, 20, 22 between upper plate 24 and lower plate 26. A tuft button simulator 28, was welded to threaded rod 30, and rod 30 was pushed through all of the mattress components, and through aligned holes 32, 34 in upper and lower plates 24, 26. Wing nut 36 was fastened to rod 30 to apply tension to the assembly and draw tuft button simulator 28 down into the foam.

A TB 603 top burner 28 was placed in the center of tuft button simulator 10, ignited, and allowed to burn for 70 seconds. Results are summarized in Table 3. TABLE 3 TUFT BUTTON SIMULATION Ex. No. FIBER BLEND FIT-FOR-USE RESULTS 43 8 osy Base blend Sample cracked within 30 seconds, (comparative example) and was fully aflame in 40 seconds. 44 8 osy Base blend and Sample cracked within 20 seconds 2.1 osy leno weave of ignition. 45 8 osy Base blend and Sample cracked within 30 seconds. Conwed scrim 46 6 osy 15% Basofil and Sample cracked within 30 seconds. Base blend 47 6 osy 15% Conex and Sample cracked within 25 seconds. Base blend 48 6 osy 15% silica and Sample did not crack, Base blend and self-extinguished in 8 minutes. 49 6 osy 15% Kynol and Sample did not crack, 85% Base blend and self-extinguished in 111/2 minutes. 50 5 osy 15% silica/ Sample did not crack, 40% modacrylic/ and self-extinguished in 12-15 minutes 45% Visil

In several previous full-mattress burns of various constructions, an 8 osy needlepunch fabric of 60% Visil/40% modacrylic had successfully passed according to the criteria set forth in California Test Bulletin 603. Only in constructions where this barrier was subjected to tension after charring was this fabric not successful. As a control, to show that known fabric performance in full scale testing performed comparably with this bench test, the 8 osy fabric was used (Ex No. 43). The sample cracked in the area surrounding the tuft button within 30 seconds, and the entire assembly was fully aflame within 40 seconds. This was the desired performance, since it accurately portrayed the performance of this fabric in full-scale burns. Ex No. 44 used the 8osy fabric in a composite with a 2.1 osy leno weave secondary carpet backing fabric. Likewise, it cracked within 20 seconds, and was withdrawn as a possible solution. Similarly, Ex No 45 used a polypropylene scrim, very light in wt (about 1 osy) that had a “leno-weave look” to it. Though it was not a woven fabric, the vertices of the “warp” and “fill” monofilaments were fused together. This sample also cracked well under 1 minute.

The remaining samples prepared were not composites, but needled blends of fibers performed on a pilot line card/crosslapper/needleloom assembly. These samples were also produced at lower weights to gain economic advantages. The first fabric evaluated, Ex No. 46, was a 6 osy fabric consisting of 15% melamine, and 85% “base blend” of 60/40 Visil/modacrylic. This fabric cracked within 30 seconds and flamed out of control. It was eliminated as a candidate for this application. Ex. No. 47, a 6 osy fabric consisting of 15% meta aramid, and 85% “base blend” of 60/40 Visil/modacrylic, also cracked and burned out of control within 25 seconds. Ex. No. 48, a 6 osy fabric consisting of 15% amorphous silica, and 85% “base blend” of 60/40 Visil/modacrylic did not crack, and the full assembly self-extinguished within 8 minutes of ignition. Similarly, Ex No. 49, a 6 osy fabric consisting of 15% novoloid, and 85% “base blend” of 60/40 Visil/modacrylic did not crack, and self-extinguished within 11.5 minutes. Though many other fibers were considered for this demonstration, the higher cost of some fibers prevented them from being considered economical. In a follow-up to these trials, a fabric according to the present invention, Ex. No. 50, a 5 osy fabric consisting of 15% amorphous silica, 40% modacrylic, and 45% Visil, was assembled in the tuft button simulator rig, and it also did not crack, and in fact, self-extinguished in about 13 minutes.

Thus, it should be evident that the use of amorphous silica fibers is highly effective in providing FR fabrics. The invention can be practiced by combining amorphous silica fibers with at least one other flame retardant fiber, but is necessarily limited thereto. Nor, is practice limited to the selection of a particular FR fiber so long as the one or more selected are combined with amorphous silica fibers. The fiber blends of the present invention can be utilized to manufacture flame retardant fabrics for a variety of purposes including, but not limited to barrier fabrics for upholstery, bedding and bed clothing applications. Moreover, the fabrics are not limited to non-woven types.

Based upon the foregoing disclosure, it should now be apparent that the use of the fiber blend described herein will carry out the aspects set forth hereinabove. It is, therefore, to be understood that any variations evident fall within the scope of the claimed invention and thus, the selection of specific component elements can be determined without departing from the spirit of the invention herein disclosed and described. Thus, the scope of the invention shall include all modifications and variations that may fall within the scope of the attached claims. 

1. A flame retardant or flame resistant (FR) fiber blend comprising: amorphous silica fibers; and at least one FR fiber.
 2. The fiber blend of claim 1, wherein said at least one FR fiber is selected from the group consisting of modacrylics, polyester with phosphalane, melamines, meta-aramids, para-aramids, polybenzimidazole, polyimides, polyamideimides, partially oxidized polyacrylonitriles, novoloids, poly(p-phenylene benzobisoxazoles), poly (p-phenylenebenzothiazoles), polyphenylene sulfides, flame retardant viscose rayons; viscose rayon containing aluminosilicate-modified silica, cellulosics, polyetheretherketones, polyketones, polyetherimides, natural or synthetic fibers coated with an FR resin, or mixtures thereof.
 3. The fiber blend of claim 1, wherein the blend comprises at least about 5 weight percent amorphous silica fibers, based upon the total weight of fibers in the blend.
 4. The fiber blend of claim 1, wherein the blend comprises from about 5 to about 65 weight percent amorphous silica fibers and from about 35 to about 95 weight percent of at least one FR fiber.
 5. The fiber blend of claim 1, comprising amorphous silica fibers, modacrylic fibers, and FR rayon fibers.
 6. The fiber blend of claim 1, comprising amorphous silica fibers, modacrylic fibers, and viscose rayon fibers.
 7. The fiber blend of claim 1, comprising amorphous silica fibers, modacrylic fibers, and cellulosic fibers.
 8. The fiber blend of claim 1, comprising amorphous silica fibers and FR rayon fibers.
 9. The fiber blend of claim 1, comprising amorphous silica fibers, modacrylic fibers, viscose rayon fibers, and FR polypropylene fibers.
 10. A barrier fabric, manufactured from a blend of fibers comprising: amorphous silica fibers and at least one FR fiber.
 11. The barrier fabric of claim 10, wherein said at least one FR fiber is selected from the group consisting of modacrylics, polyester with phosphalane, melamines, meta-aramids, para-aramids, polybenzimidazole, polyimides, polyamideimides, partially oxidized polyacrylonitriles, novoloids, poly(p-phenylene benzobisoxazoles), poly (p-phenylenebenzothiazoles), polyphenylene sulfides, flame retardant viscose rayons, viscose rayon containing aluminosilicate-modified silica, cellulosics, polyetheretherketones, polyketones, polyetherimides, natural or synthetic fibers coated with an FR resin, or mixtures thereof.
 12. The barrier fabric of claim 10, wherein the blend comprises at least about 5 weight percent amorphous silica fibers, based upon the total weight of fibers in the blend.
 13. The barrier fabric of claim 10, wherein the blend comprises from about 5 to about 65 weight percent amorphous silica fibers and from about 35 to about 95 weight percent of at least one FR fiber.
 14. The barrier fabric of claim 10, comprising amorphous silica fibers, modacrylic fibers, and FR rayon fibers.
 15. The barrier fabric of claim 10, comprising amorphous silica fibers, modacrylic fibers, and viscose rayon fibers.
 16. The barrier fabric of claim 10, comprising amorphous silica fibers, modacrylic fibers, and cellulosic fibers.
 17. The barrier fabric of claim 10, comprising amorphous silica fibers and FR rayon fibers.
 18. The barrier fabric of claim 10, comprising amorphous silica fibers, modacrylic fibers, viscose rayon fibers, and FR polypropylene fibers.
 19. The barrier fabric of claim 10, wherein said fabric is non-woven.
 20. The barrier fabric of claim 10, where said fabric is needlepunched.
 20. A flame retardant fabric, manufactured from a blend of fibers comprising: amorphous silica fibers and at least one FR fiber.
 21. The flame retardant fabric of claim 10, wherein said at least one FR fiber is selected from the group consisting of modacrylics, polyester with phosphalane, melamines, meta-aramids, para-aramids, polybenzimidazole, polyimides, polyamideimides, partially oxidized polyacrylonitriles, novoloids, poly(p-phenylene benzobisoxazoles), poly (p-phenylenebenzothiazoles), polyphenylene sulfides, flame retardant viscose rayons, viscose rayon containing aluminosilicate-modified silica, cellulosics, polyetheretherketones, polyketones, polyetherimides, natural or synthetic fibers coated with an FR resin, or mixtures thereof.
 22. The flame retardant fabric of claim 20, wherein the blend comprises at least about 5 weight percent amorphous silica fibers, based upon the total weight of fibers in the blend.
 23. The flame retardant fabric of claim 20, wherein the blend comprises from about 5 to about 65 weight percent amorphous silica fibers and from about 35 to about 95 weight percent of at least one FR fiber.
 24. The flame retardant fabric of claim 20, comprising amorphous silica fibers, modacrylic fibers, and FR rayon fibers.
 25. The flame retardant fabric of claim 20, comprising amorphous silica fibers, modacrylic fibers, and viscose rayon fibers.
 26. The flame retardant fabric of claim 20, comprising amorphous silica fibers, modacrylic fibers, and cellulosic fibers.
 27. The barrier fabric of claim 20, comprising amorphous silica fibers and FR rayon fibers.
 28. The flame retardant fabric of claim 20, comprising amorphous silica fibers, modacrylic fibers, viscose rayon fibers, and FR polypropylene fibers.
 29. The flame retardant fabric of claim 20, wherein said fabric is an open weave.
 30. The flame retardant fabric of claim 20, where said fabric is a closed weave. 